Phases of methane

Here you see Methane going through all 3 of the "normal" phase transitions we know of on Earth - as a solid, a liquid, and a gas.

What's fascinating about Methane is there is another world in our solar system with running liquid, and that is Titan - wondrous moon of Saturn. Except the liquid in question is methane, not water. As far as anyone knows now, methane acts on Titan almost exactly like water acts on Earth - it can flow, it can evaporate, it can condense, it can freeze, melt, re-freeze, and so on. Such that the surface of Titan - from above - looks very Earthlike. 

This is a false-color radar image of a slice of Titan's surface from the Cassini probe. The dark areas are what you think they are - lakes. Of methane. Not good for human swimming!

 Another radar image of Titan from Cassini, untouched.

Another Cassini image (there are so many - what a wonderful spaceship!), showing the magnificent atmosphere of Titan - thicker than Earth's. There is of course a heavy methane presence in the atmosphere.

Keep in mind through all this that the average temperatures on Titan's surface is -300F, and Titan receives about 1% of the sunlight the Earth does. So, just like Earth with water, Titan just happens to reside in a temperature belt that allows all phase transitions of methane to occur, creating everything shown above. It's pure luck, but what isn't?

Finally, to put Titan in perspective, check this out:

As you can see, Titan is quite large, and would easily be considered a planet if it was in its own orbit. However, it's not the largest moon in our solar system, as that honor goes to Jupiter's Ganymede, which is just a smidge larger than Titan.

Also too:

A methane capture system for cows (prototype). Believe it, since it's true: livestock are one of the largest sources of methane on Earth, which acts as a greenhouse gas.